There are a good number of downloads when you're mapping, so I am going to start by giving you the first one.
http://www.fileplanet.com/90429/0/0/...ion/Worldcraft The correct download should be the last one on the page and looks like this "WorldCraft v3.3
Worldcraft is a graphical level editor you can use to make your own maps for Valve Software's Half-Life. " The size is 1.9 MB and it's date is 6/10/2000. A great tutorial for the setup of Hammer is here -->
http://www.youtube.com/watch?v=uh1uC2hLY2M . This guy has all the downloads in one place, and walks you through both Steam and WON Hammer downloading/ setup. That's it for the setup once you looked at that. That was easier than we thought